A variety of vehicle-mounted devices are known for spraying herbicides, and other vehicular apparatus are known for dispensing insecticides. In general, these sprayer devices comprise a mobile frame, or carrier, supporting a reservoir, or tank, from which a chemical herbicide or insecticide solution is pumped through spray nozzles. The flow rate of sprayed material is usually controlled by means of manually operated control valves in the pipelines of the sprayer.
The mobile carrier which supports the reservoir and spraying equipment may be self-propelled, such as the sprayer devices disclosed in Erlandson, U.S. Pat. No. 2,115,199, Doerr, U.S. Pat. No. 3,038,665 and Patterson et al, U.S. Pat. No. 3,092,328. Mobile support frames lacking their own motive means are also known. In these devices the support frame is attached to another device, such as a tractor, which propels the frame and its mounted spraying equipment. Devices of this type are disclosed in Lindsay, U.S. Pat. No. 2,977,715, Taylor, U.S. Pat. No. 2,086,055 and Jordan, U.S. Pat. No. 1,462,861.
The sprayers may also be equipped with shields or "hoods", i.e., enclosures for vegetation. These may be made of rigid, semi-rigid or flexible materials, e.g., metal, plastic, wood, canvas, and the like. In insecticide sprayers, hoods typically prevent dissipation of the insecticide to unplanted areas between sprayed plants and ensure a more efficient distribution of the insecticide on plants being sprayed. In herbicide sprayers, hoods are typically used to enclose desirable plants and to prevent their coming into contact with overspray of harmful herbicide being dispersed in the vicinity.
Conventionally known vehicle-mounted herbicide spray devices have significant shortcomings. For instance, although they are equipped with a means for controlling the amount of herbicide being distributed, e.g., manually operated control valves, they are not provided with any means for accurately measuring the flow rates and amounts of herbicide being dispersed. Also, films or deposits of herbicide may be retained on the surface of the plant shields, and thus when the sprayer is moved across rows of crops or plants, for instance, toxic herbicides may rub off from the shields onto the desirable plants, and cause them to wither and die.